Gear pump



July 12, 1960 J, c, w s 2,944,487

GEAR PUMP Filed Aug. 3, 1956 r 7 Sheets-Sheet 1 2L L/QU/D SUPPLY 7'0 FREEZE/QM PA T/AL VACUUM 26 35 VINVENTOR.

c/o zz 6. waif/ 4% www- July 12, 1960 Filed Aug. 3, 1956 J. C. WALSH GEAR PUMP '7 Sheets-Sheet 2 IN V EN TOR.

J U M a W019i J. C. WALSH GEAR PUMP '7 Sheets-Sheet 3 Filed Aug. 3, 1956 J0 c. WM

I II. N E mm Na \N ww mm N y 12,1960 J. c. WALSH 2,944,487

GEAR PUMP Filed Aug. 3, 1956 7 Sheets-Sheet 4 5y L/QU/D T0 FREEZER 4\(- SUPPLY IN VEN TOR.

/ rfo zz 6 71/62 45% July 12, 1960 J. c. WALSH 2,944,487

GEAR PUMP Filed Aug. 3, 1956 7 Sheets-Sheet 5 J. C. WALSH July 12, 1960 GEAR PUMP 7 Sheets-Sheet 6 Filed Aug. 3, 1956 1 Na 3 l l MON b? QM wY/ QNN July 1960 J. c. WALSH 2,944,487

GEAR PUMP Filed Aug. 3, 1956 7 Sheets-Sheet 7 J11 J05 if IN V NTOR J37 41 1 tfafizz 6 0119i z ,944,4s7 GEAR PUMP John C. Walsh, Cedar-Rapids Iowa, assignonto'Cherry- Burrell Corporation, Chicago, Ill.,-1a corporation of Delaware p Filed Aug. 3, 1956, Ser. No. 601,863

12 Claims. (Cl. 103-7) This invention relates to mix pumps used especially in the manufacture of ice cream to blend a gas into, a liquid and pump the two fluids while ,they'are being mixed. a Y {One object of this invention is to provide amix pump wherein fluids such as air and an ice cream liquid are metered, mixed and pumpedby a unitary device.

Another object of the instant invention to provide a mix pump housing which by the exchange of arm parts may have its outputof icecream mix doubled.

A further objectof the present invention'is'It'o provide,

FigZ'j9' is a side, view 'of a mix with the cover plate, removed;

a 2,944,487 Patented July 12, 1960 shown with attachments used on ice cream making machines; V Fig. 7 is an end view of a mix pump taken on line 7-7of Fig. 6;

Fig, 8' is a side view of the mix pump shown in Fig. (Swith the channel cover and air'su'pply conduitremoved; pump shown in Fig. '6

Fig. 10 is a cross sectional view of a mix on 1ine10-.1'0 of Fig. 8; andv f Fig. 11 is acrosssectional view of a on linell-f-ll of Fig. 8.

Referring" now-to' Fig. 1 in the drawings, mix pump 20.is.connected to a liquid supplytank by a pipe 21.-

pump taken mix tall zen The liquid supplyitan k contains a mix liquid which is the basic ingredient for making ice cream. Connected to the opposite side of mix pump 20-is an air filter which provides air to the mix pump 20 through an air pipe 2 2. The'flow-sof; air to the mix pump is regulatedjby valve '23wh ichis interposed between the air filter. 'and:

themix pump. A discharge pipe 24 connects the mix a mix pump which has a minimum of parts and sea ls I so that it may beeasily cleaned. V p i: Another object of the invention herein disclosed is to provide a mix pump which may be dismantledeasily in order to facilitate cleaning and therefore be acceptable to the dairy industrya a Still another object of the invention is to design a mix pump system with no interconnecting piping.

A further object of the invention is to provide a combination mix pump system in which the mix pump and the air pump operate at constant speed with respect to each other so as to control'more accurately than heretofore the composition of the air and mix discharged therefrom. I

A still further object of the invention is to reduce the number of moving parts required to pump, blend, and meter the air and mix handled by the pump. Ice cream manufacturers are regulated as to the sani tation and quality of their products. It is important that the amount of air mixed in ice cream be controlled and that it is important to achieve a mechanism which is .easily cleaned by one who is .not necessarily a skilledmechanic.- A mix pump. which mixes air'intoan ice cream mix is required and this pump must be able to accurately measure the amount of air being mixed. Furthermore, the mixing machine must be simple so that a minimum of care is required-audit must be easily dismantled for cleaning. The means by which the foregoing and other objects are accomplished and the method of their accomplishment will readily be understood from the' following specification upon reference: to the accompanying draw ings'inwhich: I Fig. 1 shows a mixpump withseveral ofits acces sories as would be placed in an ice cream haakingmachine; I f Fig. 2 is across sectional-view of a-pump as taken online2--'2ofFig.1; t Fig. 3 is a cross sectionalview of a mix pump'as' taken on line 33 of Fig. 2; 1 I Fig. '4 is a cross sectional 'view'of'a gear pump'showlingone of the gears in the pump as taken'on line 4 4 ofFigs.1and 3; Fig. '5 is a perspective view of a filler block used-in? amix'p'ump'on themix liquid side;

'. 'Fig. 6 is a'second, modificationiofthe" mixpump' pump with the freezer unit so that the aerated mixture is conducted;from the mix pump to the freezer through pipe: 2 4.; A motor (not shown) drives a belt connected to a pulley which in turn drives the mixpurnp: f; Pump 20 consists of a housing 25 as shownin Figs. 2;;and 4 with a cover plate 26 attached thereto.- Studbolts 27 are-screwed into drilled and tapped holes'29 of; housing 25. Holes 31 inicover plate 26 register with the drilled and tapped holes 29 of housing 25 'so that cover plate 26 may be placed immediately adjacent toqhousing 25 andstuds 27 will protrude through the holes.31.. 'Nuts .28 are screwed onto bolts 27 to hold the cover plate in place.' 1 In the centerportion of housing 25,'Fig.-3, is a cylindrical center chamber 32 that has cover plate 26 forming one end thereof. Immediately adjacent to center chamber-.32 andin communication therewith is a cylin drical air chamber 33 of a diameter and height equal to'the first mentioned center chamber- 32. A cylindrical liquid chamber 34 of a diameter and height equal to the center chamber '32 is immediately adja chamber on the "side opposite the air chamber.-

*-As shown in Fig. 2, the splined end 38 of drive Shaft, 35 is rotatably mounted in bushing 36 that is press fitted into housing 25; The opposite end 39 of drive shaft 35 is; rotatably mounted in bushing 37 which is press fitted into abore 41 in cover plate 26. The drive shaft 35' is sq disposed that'the longitudinal axis of the drive cent tosaid center'chamber and 'opens into the center l shaftcoincides with the longitudinal axis of the aforem ntione e'enter chamber 32. Mounted on anenlar'ged portion 42 of drive shaft 35 is a drive spurgear 43 whose i i m tees h a p i g .6 ts s a ed t n 4 mm fi ted int a' hole i47 in 'housing 25 in sucha mannertha't {the long tudinal dis of. shaft 45 coincides with that at 'aii qharnber 33. 'fMounte'd onvthe smallerj portionfl'49 of shaft 46 is abe aring 51 and. mounted on said eafih' j n gear-. 52 ofia :face width eq ual to gdrive spurgear43 .j V -f Spur gear 52 "has ano u tside diaineterethat" PPIQ irv 51..is an air spur.

mates thediameter of air chamber 33-sothat the-top lands of teeth 53 ;may coact 'with, chamber walls 54: to

form practically a fluid tight. seal. Gear 52 is rotatably mounted on shaft ,46 and teeth S3 mesIrWith te eth- 44 a 3 a on gear '43 so that as gear 43 is rotated, gear 52 also rotates and pumps.

An enlarged portion 55 of shaft '56 is press fitted into hole 57 .in housing 25. Shaft56 has asmaller .portion sfi'whic'h has abushing '59 mounted thereon. A pumping. means, .gear 61, having half the .face width'of gear 431s rotatably mounted on shaft '56 by meanssof bushing.59 The outside diameter of mix .liquid spur :gear 61 approximates the diameter of mix liquid chamber 34 So'thatthetop lands of teeth 62 may coact with side.

walls 63' of mix liquid chamber 34.

Rigidly mounted on the smaller portion 58 of shaft 56-is a spacefiller block 64. The outsidediameter of block 64 is approximately that of mix "liquidchamber 34so that block '64 may completelyifill'the volume not taken by the gear. Block 64 hassa cut out portion .65 sothat the block does notinterfere with drive gear 43. I n-order to "keep block 64" from *turning'due to the friction between the block and gear 61, the blockhas =apin hole *66extending therethrough. Extending through a hole =68-in housing '25 is a pin 69 that extends into pin hole 66 f block 64-.

--"Connecting mix liquid chamber 34 with a liquid pipe 21 is an inlet passage 71 whichextends through housing 25. On the opposite side of the mix pump is an air inlet passage 72-in housing which connects air chamber 33, with air pipe 22. A mixture discharge passage 73 extends from the junction of center chamber 32andair chamber 33 to discharge pipe'24.

..Inoperation, the power to the mix pump is supplied from aimotor, not-shown. The motor drives the belt whichflin turn drives a pulley attached to the splined portion 38= of drive shaft v35. Since gear 43 is fixed to drive. shaft at the enlarged portion 42, the gear 43 turns with drive shaft. 35. .In turn, both gears 52 and 61 :turnwith gear =43since the teeth-ofeach of the gears mesh with gear 43. As the gears are turning, an ice cream mix liquid is fed from the liquid supply tank to chamber.34 through pipe 21 and inlet 71. As the mix liquid reaches chamber 34, it is measured into the spaces 74 formed bet-ween teeth 62 and chamber wall 63. The rotation of the gear 61 carries the liquid to center gear 43. Since spur gear 61. has :half the face width of spur gear 43, the liquid flows into the spaces 75 formed by teeth and wall of center chamber'32 instead of being squeezed out between the: gears as in the operation of the usual gear pump. Because gear 61 has half the width of gear 43, the volume of chambers is twice the volumeof chamber 74 and therefore the liquid only half fills. the chamber 75.

At. the same time that the mix liquid 'is being drawn into chamber 34, the air spur gear 52 is turning and drawing air through the air filter along air'pipe 52 through passage 72 and to chamber 33. The air fills up spaces 76 which are formed by teeth 53 and chamber wall 54 .to act as a metering means. As the gear 52 rotates, the air is carried in spaces 76 to the-point where gear 52 meshes with gear 42 and the air and mix liquid are intermingled. The meshing of the gears not only accomplishes the aeration of the mix but'also the. pumping of the aerated mix out discharge 73 to discharge pipe 24 and on to the freezer.

Since the spaces 74 have one half of the volume of spaces 76, the ratio of air to-the. liquid mix is two to one when the air is admitted .at .atmosphericpressure, and this results in an ice cream of a two hundred-percent overrun. However, it is obvious that the amount of overrun may be reduced quite simply by adjusting the valve "23 so as to limit the amount of air admitted to the chamber 76. Also, by making the face of gear 61 narrower the amount of overrun could be increased. Since overrun in the ice cream industry is generally in the range of to percent, the valve 23 would normally be partially closed to a'setting that would yield ice cream of- .the desired overrun. Itvwill be understood,'of course, thatcthis.invention afiords awide rangeof overrun control, depending on setting of the valve 23, all the way from approximately Zero, with the valve 23 closed, to about 200, with the valve 23 open. It will be seen that with this construction the amount of overrun will always be the same because the spaces are held to a very close tolerance.

The above described mix pump lends itself to a simple modification which doubles the capacity of the pump at the same percentage of overrun. The modified mix pump :of a high. capacity is described below.

'Refer-r'ing to Fig. -6, a. high capacity mix pump 100 has a pipe 101 connecting the mix pump 100 to a liquid supply tank and. air inlet pipe 102 connecting an air filter to the mix pump. A valve 103 regulates the flow of air through pipe 102. A discharge pipe 104 connects the mix pump 100 with a freezer in which the mixture is frozen to make ice cream.

Mix pump 100 which is similar to the above described mix pump 20 consists of a' housing 105 and a cover plate 106 attached thereto. As shown in Fig. 10 a housing 105 has holes 107 drilled and tapped therein and holes 108 aredrilled in cover plate 106 in registry with holes 107. Stud bolts 109 are screwed into holes 107 and cover plate 106 is placed adjacent to housing v105 so that stud bolts 109 protrude through'holes 10$. 'Nutsll'l are.'then placed onstud' bolts 109 to hold cover'plate 106 in'place.

Positioned in the central portion of housing 105, Fig. 9, is "-a cylind'rical center chamber 112. Rotatably mounted in housing 105 is a drive shaft 113 which extends through the center'portion of the chamber 112 and is also rotatab'ly mounted incover plate 106. 'Rigidly attached to drive shaft 113 is a spur gear 114 whose outside'diameteris approximately equal to the diameter of center chamber 112 and the face width is-equal to the length 'of' the chamber. Teeth 115 of driven spur gear 114 have top lands which coact with walls 116 of chamber112 to form a fluid seal.

Immediately adjacent and opening into chamber 112 is a cylindrical air chamber 118 of a length and diameter equal to said chamber 112. A shaft 117 is rigidly mounted in housing 105 so that the longitudinal axis of shaft 117 coincides with the longitudinal axis of air chamber 118. A bushing 119 is mounted on shaft 117 and a spur gear 121 is rotatably mounted on shaft 117 by means of said bushing 119. The width of gear 121 is equal to that of gear 114 and to the length of air chamber'118. Teeth 122 mesh with teeth 115 of drive spur :gear 114. The outside diameter of air spur gear 121 is approximately the diameter of air chamber 118 so that the top lands of teeth 122 coact with side walls 123 ofv the: air chamber to form a fluid seal. At the junction of air chamber 118' and center chamber 112 is an air junction 124. At the opposite side of the aforementioned junction ofrchambers .112 and 118 is a second junctionx125 known as-the discharge junction. Positioned immediately above junction 125 is an aerated mixture inlet hole 135.

Adjacenttocenter chamber 112 but on the opposite side of air chamber 118 is a mix liquid chamber 126, and at :the junction of said chambers is an air and liquidmixture junction 134. The chamber 126 opens on to center chamber 112 and is of a' diameter and length equal to the center chamber. An inlet passage 127: connects the chamber 126 and pipe 101. Rigidly connected to housing 105 andextending into chamber 126 is a shaft 128 whose longitudinal axis coincides with the longitudinal axisof chamber'126. Rotatably. mounted on shaft 128 through bushing 129 is a gear 131. The widthcf gear 131 equals thatof :drive gear 114' and the teeth 132 mesh with-teeth 115 ofizthe driveigear 114. The top lands ofteethl132 coact with walls 133 of chamber 126 to form a fluid tight seal. a

An air inlet orifice 136 in cover plater106 is positioned in; registry with: air junction 124. .Discharge passage .137

and inlet 138 provides a duct from junction 134 to pasv sage 135 adjacent to junction 125.

In operation, power issupplied to mix pump 100 by a belt drive, connected with drive shaft 113 which rotates drive gear 114. Since the teeth of gears 114, 121, and 131 are interconnected in operation they all rotate at the same speed. Mix liquid is supplied to pumping and metering means in chamber 126 through inlet 127 and into the spaces 143 between teeth 132 and chamber wall 133.

At the same time that liquid is being fed to mix liquid chamber 126, air is supplied to air junction 124. As the gears rotate, the air flows into spaces 144formed between teeth 122 and walls 123 and into the spaces 145 for-med between teeth 115 and wall 116 so that the spaces 144 and 145 constitute metering means. "Asgear 114rotates, the air spaces 145 move toward junction 134 and as gear 131 rotates, spaces 143 move toward junction 134. At junction 134, the air and liquidmeet in equal volumes. The air and liquid are not only mixed at junction 134 but are also pumped outthrough hole 137 by the mesh-v ing of the teeth in gears 114 and 131. The constantm'eshing of teeth 115 and 132 pumps the mixture of'anequal volume of air and equal volume of mix liquid through discharge passage 137 along channel 139 and then-out through orifice 138.

As the mixture of an equal volume of air and mix liquid is discharged to passage 135 and then into discharge passage 146, the equal volume mixture meets with more air which comes up from junction 125. The

air is pumped into the air liquid mixture and thus the additional air is blended into the mixture. The mixture with a greater content of air is then pumped through exhaust passage 146 and to discharge pipe 104 which takes the mixture to the freezer.

As may be seen, since gears 114, 121, and 131 are of equal size the teeth must be of equal size which there-' fore means that air spaces 143, 144, and 145 are also of equal size. The air space 143 fills with a given amount of liquid and space 145 fills with an equal amount of air. At junction 134 the equal amounts of air and liquid are mixed and pumped along the duct portion to the dis charge passage 135. At the discharge passage and junction 125, one hundred percent more air is added to the mixture which results in an ice cream that has a two hundred percent overrun when the mixture is frozen in the freezer. 7 r

A further advantage should be noted that the basic housing used for the first described mix pump may be used for this second described mix-pump. To convertfrom the lower capacity mix pump to the higher capacity mix pump the air line is simply removed and replaced by a plug, thecover plates are exchanged-and the gear one end of said chamber formed by the cover plate, a drive spur gear in said center chamber with the top lands of the teeth coacting with the chamber walls in a' fluid tight seal, a drive shaft attached to the drive.

spur gear on one end and the other end attached to a source of motive power, a cylindrical air chamber in said housing connecting to the center chamber and the diameter and height of said air chamber equal to that of the center chamber, an air spur gear in said airchambe'r with the top lands of the teeth coacting with chamber Walls in a fluid tightseal andmeshing with the drive spur in the mix liquid chamber is replaced. Thereby the capacity of the IIIiXI Pump is doubled. 7

While I haveshown and described particular embodimerits of my invention, it will occur to thoseskilled in theart that variations, changes,--and modifications may be made without departing from my invention and PI therefore aim in the appended claims to cover'all such changes and modifications asfall' the true spirit and scope of my invention.

' 1. In a device of the character described comprising a housing, a cover plate. attached to. said housing, a cylindrical center chamber in the central portion of said housing and the longitudinal axis of the center chamber and housing substantially perpendicular to each other and gear, a cylindrical mix chamber in said housing con- I meeting to the center chamber, the diameter of said mix chamber equal to that of said center chamber, the height of s'aid mixchamber equal one half that of the center chamber, a mix spur gear in said mix chamber and the top lands of the teeth coacting with the walls of the chamber to form a fluid tight seal, a mix liquid passage opening into ,themix chamber remote from the center chamber, an air inlet passage opening into the air, cham her and a liquid air mixture discharge passageway opening to the junction of said air and center chambers. ,2. A'mix'pump for blending mix liquid with air in the manufacture ofice cream comprising a housing, a cover plate, a cylindrical air chamber in said housing.with the cover plate forming one end thereof, an air inlet pas sage opening into said 'air chamber, a shaft mounted on said housing and extending into said'air chamber, 'an airspur gear mounted on said shaft and' the top lands ofjthe teeth coacting withithe chamber wall' to form a fluid seal, a cylindrical'center chamber in the housing opening into the air chamber, a drive shaft rotatably mounted in said housing extending into said center chamber,.a drive spur 'gear attached to said drive shaft meshing with the air spur gear and the top lands of the teeth coacting with the center chamber to form a fluid tight seal, a discharge passage extending from the junction of the .air chamber and center chamber to the outer surface. of the housing, a cylindrical mix liquid chamber in saidhousing opening into the center chamber having one half the height of said center chamber, a second shaft mounted .in said housing and extending into the mix liquid chamber, a liquid spur gear rotatably mounted on said second shaft having an equal number of teeth to that on the drive spur gear and the top lands of the teeth coacting with the mix liquid chamber wall to form a fluid tight seal, and a mix liquid inlet passage to said mix liquid chamber remote from said center chamber.

3. A mix pump for blending mix liquid with air in the manufacture of ice cream comprising'a housing, a cover chamber, a mix liquid inlet passage opening into the mix liquid chamber, a second shaft mounted in said housing extending into the mix liquid chamber, a mix liquid spur gearfmouhted on said second shaft and meshing with said center spur gear, a cylindrical air chamber opening into the center chamber and having a'height and" diameter equal to that of said center chamber, an air inlet passageopening into the juncture of the air and center chambers, mix'liquid air mixture discharge passage in said housing opening from the junction of the air and center chambers, a third shaft mounted in said housing and extendinginto the air chamber, an air spur gear mounted on' said shaft, a mix liquid air mixture conduit from the j junction of the mix liquid and center chambers to the dischargepassage. Q v

4. A device of the "character described comprising a housing, a cover plate, fastening means holding the cover plate to the housing, a liquid air mixture inlet hole in the cover plate, a liquid mixture exit hole in the cover plate,.a channel connecting the liquid air mixture inlet and exit. holes, a channel cover .plate attached to the cover plate covering the channel and holes entirely, a cylindrical mix liquid .chamber in the housing with the coverfpl'ate forming one end thereof, a shaft mounted in saidhousing, aliquid gear of an outside diameter slightly smaller than the diameter of the liquid chamber and the width of the gear slightly less than 'thechamber height, a mix'liquid inlet passage in the housing opening into-the liquid chamber, a cylindrcial center chamber of equal height and diameter tofthe liquid chamber and opening between said chambers, a drive shaft rotatably mounted in'the housing extending through said center chamber, a drive gear of equal width and outside diameter to the liquid gear attached to said drive. shaft in the center chamber, a junction between the center and liquid chambers, an air chamber of equal height and diameter to the liquid chamber opening into the center chamber, an air junction adjacent the opening between the air and center chambers, a discharge junction opposite the air junction and adjacent the opening between the air and center chambers, a discharge passage in the housing extending from said dis charge junction, a second shaft mounted in the housing extending into the air chamber, and an air spur gear of a Width and outside diameter equal to that of thedrive gear rotatably mounted with relation to the housing mounted on the second shaft.

5. A gear pump comprising a housing having three substantially circular, intercommunicating chambers therein, two being end chambers communicating relatively diametrically with a center chamber, a gear in each of said chambers, the gears in' the end chambers being meshed with the gear in the center chamber, a first fluid inlet port in said housing communicating with one of said end chambers remote from the center chamber, a second fluidinlet port in said housing communicating with the other of said end chambers, a single outlet port in said housing for said fluids, said outlet port communicating with the center chamber and the second fluid end chamber adjacent the meshing of the gears in said chambers, and means for transmitting the first fluid from its end chamber to said outlet port.

6. A pump as described comprising a housing three substantially cylindrical chambers therein so positioned and intercommunicating that one serves as a center chamber and the other two are end chambers, a gear in' each of said chambers, the center gear meshing with the two end gears, the top lands of the gear teeth co-acting with the chamber walls to act as a fluid seal, an inlet passge to one of the end chambers remote from the center chamber, an inlet passage to the other end chamber, a single discharge passage at the juncture of the center chamber and an end chamber, and means for communicating the other end chamber with said discharge passage.

7. A pump as described comprising a housing, three substantially cylindrical chambers therein so positioned and intercommunicating that one serves as a center chamber and the other two are end chambers, a gear in each of said chambers, the center gear meshing with the two end gears, the top lands of the gear teeth co-acting with the chamber walls to act as a fluid seal, an inlet passage to one of the end chambers remote from the center chamber, an inlet passage to the other end chamber, a single discharge passage at the juncture otthe center chamber and an end chamber, and a passage in said housing for communicab' ing the other end chamber with said discharge passage.

8. A fluid pump as described comprising a housing, three substantially cylindrical chambers therein so positioned and intercommunicating that one serves as a center chamber and other two are end chambers, a gear in each of said chambers having the top lands of the gear teeth V .8 co-acting with the chamber walls to act as a fluid'se'al, the gear in -the center chamber meshing with the gears fin "the end chambers, "the; gear in the center chamber and oneiof the end chamb'ersbeing of substantially equal face width while the gear in the other chamber has 'a' face width'le'ss thanrthat of the other two gears, an inletpassage to one of the end chambersremote from "the center chamber, an inlet passage to the other end chamber, and a single discharge passage at the juncture at 'the center chamber and the end chamber having the gear of equal face width whereby the fluid is transferred from the gear of lesser face width to the center gear'and thereby to said discharge passage. g

9. vApump as described comprising a housing, three substantially cylindrical chambers of equal height therein so positioned and intercommunicating that'one 'servesa center chamber and. the .othertwo are end chambers, a gear ineach of said chambers, the gear in the 'center'chamber meshing with the gears in the end chambers, thejgear in the center chamber and one 'of'said end chambers being of a face width equalto the height of their respective chambers, the gear'in the otherend chamber being ofia face width less than the height 'of its respective chamber, a filler block in said last mentioned end chamber, said filler block being of a thickness equal to theheight of the chamber less the face width or" the gear in said chamber, the top lands of the teeth of said three gears co-acting with the respective chamber walls to act as a fluid seal, an inlet passage to each of the end chambers remote from the'center chamber, and a single discharge'passage at the juncture of the center chamber and the end chamber containing the gear of equal face width to that of the center chamber gear.

'10. A gear pump comprising a housing having three substantially circular intercommunicating chambers there'- in, two being end chambers communicating relatively diametrically with the center chamber, a gear in each of said chambers, the top lands of the gear teeth coacting with the respective chamber walls to act as a fluid seal, the gears in the end chambers being meshed with the gear in the center chamber, a first fluid inlet port in said housing communicating with one 'of said end chambers remote from the center chamber, a second fluid inlet port in said housing communicating with the other of said end chambers, a single outlet port in said housing for said fluids, said outlet port communicating with the center chamber and the second fluid end chamber adjacent the meshing of the gears in said chambers, and means for transmitting the first fiuid from its end chamber to said outlet port.

11. The gear pump of claim 10 in which the means for transmitting the first fluid from its end chamber to said outlet port comprises a passageway formed in the housing from a point adjacent the meshing of the gears in the center chamber and the first fluid end chamber and a point in the outlet port.

12. The gear pump of claim 10 in which the means for transmitting the first fluid-from its end chamber to said outlet port comprises the gear in the first fluid end chamber, said last named gear having a face-width less than the face width of the gear in the'center chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,585,731 Oakes May25, 1926 1,902,315 Vogt Mar. 21, 1933 1,937,367 Vickers Nov. 28,1933

2,079,375 McCollum May 4,1937

FOREIGN PATENTS 7 622,862 France June 9, 1927 638,325 Great Britain June 7, 1950 

